From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F72FC64EAD for ; Tue, 9 Oct 2018 14:27:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E0BC2213A2 for ; Tue, 9 Oct 2018 14:27:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0BC2213A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726649AbeJIVpA convert rfc822-to-8bit (ORCPT ); Tue, 9 Oct 2018 17:45:00 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:43621 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726393AbeJIVo7 (ORCPT ); Tue, 9 Oct 2018 17:44:59 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1g9sz8-0005ij-Vn; Tue, 09 Oct 2018 16:27:43 +0200 Date: Tue, 9 Oct 2018 16:27:42 +0200 From: Sebastian Andrzej Siewior To: Dmitry Vyukov Cc: Clark Williams , Alexander Potapenko , kasan-dev , Linux-MM , LKML , linux-rt-users@vger.kernel.org, Peter Zijlstra , Thomas Gleixner Subject: Re: [PATCH] kasan: convert kasan/quarantine_lock to raw_spinlock Message-ID: <20181009142742.ikh7xv2dn5skjjbe@linutronix.de> References: <20180918152931.17322-1-williams@redhat.com> <20181005163018.icbknlzymwjhdehi@linutronix.de> <20181005163320.zkacovxvlih6blpp@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-10-08 11:15:57 [+0200], Dmitry Vyukov wrote: > Hi Sebastian, Hi Dmitry, > This seems to beak quarantine_remove_cache( ) in the sense that some > object from the cache may still be in quarantine when > quarantine_remove_cache() returns. When quarantine_remove_cache() > returns all objects from the cache must be purged from quarantine. > That srcu and irq trickery is there for a reason. That loop should behave like your on_each_cpu() except it does not involve the remote CPU. > This code is also on hot path of kmallock/kfree, an additional > lock/unlock per operation is expensive. Adding 2 locked RMW per > kmalloc is not something that should be done only out of refactoring > reasons. But this is debug code anyway, right? And it is highly complex imho. Well, maybe only for me after I looked at it for the first time… > The original message from Clark mentions that the problem can be fixed > by just changing type of spinlock. This looks like a better and > simpler way to resolve the problem to me. I usually prefer to avoid adding raw_locks everywhere if it can be avoided. However given that this is debug code and a few additional us shouldn't matter here, I have no problem with Clark's initial patch (also the mem-free in irq-off region works in this scenario). Can you take it as-is or should I repost it with an acked-by? Sebastian